Radio transmitter-receiver switching system



RADIO TRANSMITTER-RECEIVER SWITCHING SYSTEM April 29, 1947.

J. E. K EISTER Filed June 10, 1943 e t F .6 e m K n B e S v e n m b I H a .5050 J-l J QEQQ 052m .5650 C I @323 v .nv

bg HIS Attorney.

Patented Apr. 29, 1947 N D ES PATENT oFeiicfE;

RADIO TRANSMITTER- RECEIVER: SWITCHING SYSTEM" James E; KeistenjS'cotia, N. Y., assignor to General Electric Company, a corporationof New York Applicationlunelm 1943, Serial No. 490,249

6 Claims.

. The present invention relatesto radio -equipment having a transmitting and areceiving. circuit connected to a common antenna.-

Ansobject of my inventionlisto provide an.

improved arrangement for confining the transmitted and received signals .tothe respective circuits; The novel features which I believeto be .characteristicofmy inventionare set forth transmitter l and a receiver respectively connected by concentric transmission lines 3-and A throughajunction 5 to a paraboloid antennae. The transmitter comprises a reentrant cavity oscillator having an ultra high frequency triode'l which is shown in elevation with the cathode 8, grid 9, and anode l3 diagrammatically indicated in dotted lines.- The cathode 8 is capacity coupled to a metal shell H connected at 12 to an'outer metal: cylinder l3; the grid disconnected toa concentric inner metal-cylinder I4 and the anode I0 is connected'lby sliding contact lli to-axially movable metal rod' l6 carrying a tuning disk I! having a flange l8 capacity-coupled to the outer cylinder 13. The tuning of the oscillator is varied by moving the rod It in and out.

The receiver has an annular cavity l9 and an associated ultra high frequency triode 23 shown in elevation with the cathode 2!, grid 22, and anode 23 diagrammatically indicated in dotted lines. The cathode 21 is capacity coupled as indicated at 24', to a metalshell' 25 telescoped within an upstanding "sleeve 25"at the center of the cavity I 9; the grid 22 is connected to a terminal flange 2'5 engaging contact fingers 28 on a grounded plate 29 which servesas the bottom wall of the. cavity; and the anode 23 isiconnectedto a terminal 30." The transmission line 4 islcoupled to the cavity 19 through'a loop 3| 'connected'between the grounded plate 29 and the center conductor of the transmission line. A similar coupling loop 32 is connected through transmission line 33 to a local oscillator 34.

The transmitter oscillator is driven by a pulsing circuit 35 connected between the rod l5 and the cylinder l4 and reacting with the device I so as to 2 supply pulse voltages 36 at the desired repetition rate, causing'corresponding pulses of radio frequencyoscillations 31. The transmitter oscilla-- tions are picked up by a loop 38 in the anode grid cavity and'conducted to the antenna along the transmission line 3. The transmitted pulse, upon reaching the junction of the transmission lines 3 and 4, divides, part flowing to the antenna 6 and the remainder flowing along the transmission line 4; The part of the transmitted pulse flowing along the transmission'line 4 is wasted and may damage the receiver; This part is kept to a minimum by connecting the'cathode 2| to the pulsing circuit 35 so as to apply a positive pulse coincident with the transmitted pulse suincient' to bias the triode 20 off during transmission. Whenthe tri'ode is non-conducting, the flow of ener ythrough the triode to the receiver is prevented'and the transmission line is terminated at the'receiver end by the coupling loop 3f. By means of a line stretcher 33 .by which the length ofthe line may be adjusted to desired lengths,

thetransmission' line 4 is tuned'to an odd multiple through'the transmission lined to the receiver.

Sincethe receiver'triode 20 is conducting, the termination of thetransmission line i new con-- sists of the-impedance of the loop 36 and the impedance coupled to the loop through the mode 20; This changes the tuning of the transmission line 4 so that it no longer presents a high imped ance to the flow of energy from the junction 5. During receiving the transmitter triode '5 is iased oiljpreventing theflow of energy from the coupling 1cop-'-38"through' the trickle. By means of a'linestretcher 4B thetransmission-line"3 is tuned-to an'oddmultiple of quarter wavelengt so that the shortcircuitoffered by the coupling loop 38 causes a high impedance-to-appear at the junction 5.

In the present equipment, the transmitter and receiver are at all times connected to the antenna through transmission lines and yet, Without the use of any auxiliary devices, the transmitted and received si nals are confined to the respective circuits.

The received signal is mixed in the cavity l9 with radio frequency waves from the local oscillator 34 to produce a beat frequency which is fed through an IF amplifier 4|, a detector 42, and a pulse amplifier 43 to a cathode ray tube 44. The received pulses are coordinated with the transmitted pulses by means of a sweep circuit 45 keyed by the pulsing circuit 35 so as to display the desired information.

While I have shown particular embodiments of my invention, it will be understood that many modifications may be made .without departing from the spirit thereof, and I contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a receiver having an input circuit with an electron discharge device having a control grid, the eifective grid bias of said device being adjustable between values permitting and preventing the flow of signals through the receiver, a transmission line having one end coupled to the receiver input circuit and the other end connected to a transmitter and to an antenna, said transmission line having a length such that when said grid bias is adjusted respectively to permit and to prevent the flow of signals through the receiver a low and a high impedance respectively appears at said other end of the transmission line, and keying means for causing the transmission of signals and the adjustment of said grid bias to a value preventing the fiow of signals through the receiver whereby a high impedance is ofiered to the flow of the transmitted signals to the receiver.

2. In combination, a cavity resonator including a grid controlled electron discharge device, the grid bias of said device being adjustable to values permitting and preventing the transfer of energy between parts of said cavity resonator through said device, and a transmission line having at one end a coupling loop within said cavity resonator, said transmission line being of such length that under conditions in which the grid bias prevents the transfer of energy in the cavity resonator, a high impedance appears at the other end of the transmission line to the flow of energy toward said cavity resonator.

3. In combination, an antenna, an electron discharge device having a control electrode, an

anode and a cathode, and circuit means to produce oscillations by action of said device, a second electron discharge device, transmission lines extending from each of said devices to said antenna, whereby oscillations generated by action of said first device are supplied to said antenna and oscillations received on said antenna are supplied to said second electron discharge device, means including said second device to translate said received oscillations, means to control said devices to produce low impedance alternately across the adjacent ends of the respective transmission line associated with said devices, said lines having such length that said lines alternately present high impedance to oscillations supplied to the opposite ends thereof. r

4. In combination, a transmitter including a cavity resonator and circuit elements coupled 4 therewith through a bias controlled discharge device, a receiver including a cavity resonator and circuit elements coupled therewith through another bias controlled discharge device, transmission lines leading respectively to the transmitter and to the receiver resonators from a junction for connection with a channel for transmission and reception, and bias control means for said devices for alternately turning the transmitter and receiver on and off, said transmission lines being of such length that when the bias on one of said devices is adjusted to interrupt the current flow therein a high impedance appears at the junction to the flow of energy toward the resonator coupled to said device.

5. In combination, equipment for transmitting pulses of wave energy and equipment for receiving echoes of the transmitted pulses, each of said equipments including a cavity resonator and circuit elements coupled through an associated discharge device controlling the fiow of energy through the respective equipment, transmission lines leading respectively from the resonators of said transmitting and receiving equipment to a junction through which the transmitted and received energy flows, control means for said devices alternately interrupting current flow in the devices at the desired repetition rate, said transmission lines being of such length that when a respective device is non-conducting a high impedance appears at said junction to the flow of energy toward the cavity resonator of said respective device.

6. In combination, a receiver having an input circuit with an electron discharge device having a control grid, the effective grid bias of said device being adjustable between values permitting and preventing the flow of signals through the receiver, a transmission line having one end coupled to the receiver input circuit and the other end connected to a transmitter and to an antenna, said transmission line having a length such that when said grid bias is adjusted respectively to permit and to prevent the flow of signals through the receiver a low and a high impedance respectively appears at said other end of the transmission line, and means for pulsing the transmitter and simultaneously adjusting said grid bias for the duration of the pulses to a value preventing the flow of signals through the receiver whereby a high impedance is offered to the ffow of the transmitted signals to the receiver.

JAMES E. KEISTER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,270,771 Schonfeld Jan. 20, 1942 2,211,003 Conklin Aug. 13, 1940 2,189,549 Hershberger Feb. 6, 1940 FOREIGN PATENTS Number Country Date 358,917 British Oct. 14, 1931 113,233 Australian June 2, 1941 

